Hypoventilation

Hypoventilation is a medical condition marked by slow and ineffective breathing. Also referred to as respiratory depression or hypoventilatory syndrome, hypoventilation results in abnormal retention of carbon dioxide (CO₂) in the blood because of an inadequate exchange of CO₂ and oxygen in the lungs. Patients experiencing hypoventilation typically have slow and shallow breathing and other mild symptoms that may worsen as the condition progresses. Severe hypoventilation that is not properly treated can lead to serious consequences, including heart attack, brain damage, coma, or death. There are many potential causes of hypoventilation, including conditions affecting brain and central nervous system functions, stroke, sleep apnea, or the use of certain medications or other substances that impair the brain’s ability to function normally. While the best form of treatment for hypoventilation varies based on the cause, some common treatment options include oxygen therapy, inhaled medications, and mechanical ventilation.

Background

Hypoventilation is a respiratory system disorder. The respiratory system is a network of organs and tissues within the body that allows a person to breathe and absorb oxygen from the air. It also serves to remove waste gases like carbon dioxide from the body through exhalation and to protect the airways from harmful substances and irritants.

The major parts of the respiratory system include the mouth and nose, sinuses, pharynx, trachea, bronchial tubes, and lungs. The mouth and nose are the openings through which air is pulled into the body. The sinuses are hollow spaces within the head that regulate the temperature and humidity of inhaled air. The pharynx is a tube in the throat that delivers air to the trachea. Also known as the windpipe, the trachea is a passageway through which air travels in and out of the lungs. The lungs are a pair of organs that extract oxygen from inhaled air and pass into the bloodstream. Muscles like the diaphragm and bones like the ribs also play an important part in the respiratory system. In addition, there are a number of smaller components that contribute to the process of respiration. The alveoli are small air sacs in the lungs where oxygen and carbon dioxide are exchanged. Bronchioles are branches of the bronchial tubes that connect to the alveoli. Capillaries are tiny blood vessels in the alveoli walls that move oxygen and carbon dioxide.

Under normal circumstances, the breathing process begins when air is inhaled through the nose or mouth and travels down the throat into the trachea. From there, air passes into the lungs through the bronchial tubes and enters the bronchioles and alveoli. In the alveoli, oxygen passes through a mesh of capillaries into the bloodstream. At that point, oxygenated blood goes to the heart to be pumped throughout the body. Upon receiving oxygen from the blood, the body’s various cells and tissues exchange it for carbon dioxide. A waste gas, carbon dioxide is delivered back to the lungs through the blood and is removed from the body through exhalation. All of this means that normal breathing is essential to good health.

Overview

Hypoventilation is a breathing disorder that limits the respiratory system’s ability to ensure an adequate exchange of oxygen and carbon dioxide. Normally, oxygen and CO₂ are exchanged at a balanced rate so that there is never too much or too little of either gas in the blood. In the event of hypoventilation, slow and ineffective breathing leaves the body unable to remove enough carbon dioxide, which results in poor oxygen use by the lungs. In short, a person experiencing hypoventilation has an elevated level of carbon dioxide and a lower-than-normal level of oxygen.

The primary symptom of hypoventilation is slow and shallow breathing. While the normal breathing rate is about twelve to twenty breaths per minute, the breathing rate of a person experiencing hypoventilation can drop to as low as eight to ten breaths per minute. Other mild symptoms of hypoventilation include fatigue, daytime sleepiness, shortness of breath, and depression. As hypoventilation progresses and the body’s carbon dioxide level increases, more serious symptoms such as cyanosis, headaches, confusion, and seizures may develop. In severe cases, hypoventilation can lead to respiratory acidosis, a potentially fatal buildup of acid in the body that may result in organ failure. Untreated hypoventilation can also be fatal if it leads to reduced heart rate, heart attack, respiratory illness, brain damage, or coma.

There are many possible causes of hypoventilation. Most are related to medical conditions that affect brain and central nervous system functions, other pre-existing conditions, or the effects of certain medications or other substances. Patients who have neuromuscular disorders are at particular risk of hypoventilation because they often have weakened respiratory muscles and poor muscle control. Certain chest wall deformities can cause hypoventilation when they place physical limitations on lung function. Obese patients with excess weight around the neck, chest wall, and abdomen may be prone to a type of hypoventilation called obesity-hypoventilation syndrome (OHS). Brain injuries and neurological disease that disrupt the brain’s ability to control breathing can also result in hypoventilation. Many patients with sleep apnea, including obstructive sleep apnea (OSA) and central sleep apnea (CSA) experience hypoventilation as well. The same is true of patients with chronic lung diseases like chronic obstructive pulmonary disease (COPD) or cystic fibrosis. Elevated ammonia levels due to liver disease or genetic conditions are another cause of hypoventilation. Finally, hypoventilation can also be a side effect of large doses of certain medications and other substances that interfere with brain function and depress the central nervous system. Some of these medications and substances include sedatives, narcotics, opioids, alcohol, barbiturates, and benzodiazepines.

Treatments for hypoventilation are typically aimed at improving ventilation by resolving the underlying problem. As such, treatment methods vary depending on the cause. Some common treatments for hypoventilation include oxygen therapy, use of a continuous positive airway pressure (CPAP) or bi-level positive airway pressure (BiPAP) machine during sleep, corrective surgery, weight loss, inhaled medications, mechanical ventilation, and intravenous or oral fluid therapy. When hypoventilation is caused by a medication or other substance, stopping the drug in question and undergoing detoxification, if necessary, often helps restore normal breathing.

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